A thrust lever is widely applied in the single axis of a dependent suspension of heavy trucks or passenger carriages or in dual rear axle of heavy vehicles, wherein it connects the vehicle frame with the vehicle axle. Its functions are: to ensure the relative positions of the vehicle frame and the vehicle axle, to transmit all kinds of forces and torques brought by the vehicle frame and the vehicle axle, to ensure the motion profile of the vehicle axle, etc. Therefore, a thrust lever influences directly the operation stability, smoothness as well as the comfort of passengers of a vehicle.
Nowadays, a thrust lever ball hinge works together with a thrust lever ball head in the following ways:                1. The ball hinge cooperates with the ball head via interference fit in order to satisfy the functions of the thrust lever.        2. The ball hinge is limited inside the ball head via an internal circlip or a shaft clamp ring to satisfy the functions of the thrust lever.        
In the first way, there exist two different cooperation ways: for the interference fit for the metal coat, the magnitude of interference should be reasonably designed. Otherwise, the ball hinge coat or the ball head cavity can be damaged. In addition, the coat needs to be thick enough in order to ensure enough interference fit. Otherwise, axle displacement might occur. This increases costs and disobeys the light weight concept. Regarding interference fit for elastic bodies, it needs not only suitable contours and magnitude of interference, but also good anti-abrasion property and resilience of the elastic body. In addition, the adhesive strength between the metal core shaft and the inner shaft needs to be strong enough in order to satisfy the functions of the thrust lever. Otherwise, the press-fit rubber might detach from the metal, press-fit is asymmetric, and the press-fit efficiency is low. During the long-term use, since the rubber bears different static-dynamic load, the rubber can creep and its ability to bear load decreases. Axle displacement can occur.
In the second way, the requirements for the size, the material, the degree of roughness of the surface and the surface treatment are high. The cooperation size among the ball hinge, the ball head and the ring needs to be rationally designed in order to prevent the ring from falling off which disables the thrust lever. The self-lock structure of the ring usually has a complicated structure, which is complicated to assemble. The press-fit can easily be out of place which renders it invalid.
It can be seen that the above two traditional assembling methods of a thrust lever ball head assembly have the following drawbacks: complicated structure, low assembling efficiency, high costs, heavy weight, difficult maintenance, difficult to test qualification, etc.